Friday, March 22, 2019

Exposing a K8S Service of Type LoadBalancer on Local Machine

As we had been exploring in this blog, there are different ways of installing and using K8S. It can be in the Cloud, In-Premise and also on your Laptop. For the sake of trying different things I prefer installing it on the Laptop as I would have complete control over it (building and breaking) and also also that I can work offline. And there is no cost associated with it. But, there are a few disadvantages of it, like not being able to integrate with the different Cloud services. We will look at one of the disadvantage of installing K8S on the Laptop and a workaround for the same.

When we create Pods then an IP address is assigned to them and when a Pod goes down and a new one is created by the Deployment automatically, then the Pod might be assigned a different IP address. So, when the IP address is not static then how do we access them? This is where a K8S Service comes into play. More about the K8S Service and the different ways they can be exposed here, here, here and here.

Based on how we want to expose a Service depending on the access type, Service can be exposed using Type as a ClusterIP, NodePort or a LoadBalancer as mentioned here. When a Service of Type LoadBalancer is created, then K8S will automatically creates a Cloud vendor specific Load Balancer. This is good in the Cloud, but what happens when we create a Service of Type LoadBalancer in a non-Cloud environment as in the case of Laptop where a Load Balancer can't be provisioned automatically. This can be addressed using MetalLB which is described as a 'bare-metal load-balancer for K8S'.

So, lets get into the sequence of steps to get around this problem using Metallb.

Step 1: Create a file nginxlb.yaml with the below content. This basically creates a Deployment and a Service for nginx.
apiVersion: apps/v1beta2
kind: Deployment
  name: nginx
      app: nginx
        app: nginx
      - name: nginx
        image: nginx:1
        - name: http
          containerPort: 80

apiVersion: v1
kind: Service
  name: nginx
  - name: http
    port: 8080
    protocol: TCP
    targetPort: 80
    app: nginx
  type: LoadBalancer
Create another file layer2-config.yaml with the below content. This creates a ConfigMap with the IP address range pool which can be assigned to the Load Balancer. Note that the IP address range has to be modified according to the network to which your Laptop has been connected to.
apiVersion: v1
kind: ConfigMap
  namespace: metallb-system
  name: config
  config: |
    - name: my-ip-space
      protocol: layer2
Step 2: Create a Deployment and Service using the 'kubectl apply -f nginx' command. Notice that the EXTERNAL-IP is specified as <pending> because in the local setup a Load Balancer cannot be created as in the case of Cloud.

Step 3: Delete the Deployment and the Service as they will be installed later again with MetalLB setup completed using the 'kubectl delete -f nginxlb.yaml' command.

Step 4: Install the MetalLB and the related components using 'kubectl apply -f' command.

Make sure that the corresponding Pods are created using the 'kubectl get pods -n=metallb-system' and also that they are in the Running status after a few minutes.

Step 5: Apply the configuration for the MetalLB installation using the 'kubectl apply -f layer2-config.yaml' command. In this file we specify the range of IP address from which the Load Balancer will get an IP address. Don't forget to change the IP address in the file, based on the network the Laptop is connected to.

Step  6: Now that MetalLB setup has been done. Recreate the Deployment and the Service using 'kubectl apply -f nginx.yaml'. Notice in the output of the 'kubectl get svc' command, the EXTERNAL-IP is and not <pending> as was the case earlier.

Step 7: Now that the Load Balancer has been created, open the URL in a browser to get the below nginx page. Note to change the IP address based on the above step. Now, we are able to setup a Service of Type set to LoadBalancer if we get the below page.

Step 8: Finally delete the nginx Deployment/Service and the MetalLB related components using the 'kubectl delete -f nginxlb.yaml' and the 'kubectl delete -f' command. This is an optional step, just in case you want to delete it.



By default in a non-Cloud environment when we create a service with Type set to LoadBalancer the EXTERNAL-IP is set to <pending> as a Load Balancer cannot be created. But, in this blog we have seen how to configure a Layer 2 Load Balancer (MetalLB) on the Laptop to get a Load Balancer created. Below is the screen shot before and after the MetalLB setup has been done. Note the value of the EXTERNAL-IP.



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